The following background description comprises a description of the background to the present invention and thus does not necessarily constitute prior art.
Modern-day combustion engines can use various kinds of fuel, for example diesel, petrol or ethanol. Various types of a particular kind of fuel can also be used, such as different types of diesel, with a varying content of biodiesel. Various blends of fuels, such as diesel mixed with FAME (Fatty Acid Methyl Ester) can also be used in combustion engines. The various kinds, various types and various blends of fuels can all be viewed as different grades or qualities of fuel. Therefore, the concept of fuel quality includes the various kinds of fuel, the various types of fuel and the various blends of fuel. These different kinds, types and/or blends of fuel, are fuel qualities or grades, which have different properties affecting a large number of parameters in an engine system as well as other systems, for instance in a vehicle. A variety of fuel qualities can be replenished on different refuelling occasions, possibly making it difficult for a control system as well as the driver to know which fuel quality is in the fuel system on that occasion.
For example, different fuel qualities have different energy values, which affects parameters relating to e.g. engine output, engine torque and exhaust emission control for an engine powered by such fuel. The engine output and engine torque, in turn, affect a number of parameters relating to e.g. speed regulation, cruise control and automatic gear change in, say, a vehicle.